While it is possible to make changes to a vSAN cluster outside of VxRail Manager (e.g. add storage or nodes) this is not advised (and Dell-EMC state unsupported) as VxRail Manager will not be aware of the changes.

Only changes such as adding/removing nodes/hardware components etc. may have an impact with regard to VxRail Manager - changes that are normal vSphere operations such as enabling/disabling/editing HA/DRS shouldn't have any impact. Think of it as having an inventory-management role and it makes more sense.